2 pencils cost $2.54. Which equation would help determine the cost of 6 pencils?
Solution: There are several equations that could help determine the cost, each with a slightly different approach. We know the cost of 2 pencils. We want to know the cost of 6 pencils. We can write the numbers of pencils as a proportion: $\dfrac{2}{6}$ We know 2 pencils costs $2.54. We can let $x$ represent the unknown cost of 6 pencils. The proportion of these costs can be expressed as: $\dfrac{\$2.54}{x}$ The cost changes along with the number of pencils purchased, and so the two proportions are equivalent. $\dfrac{2}{6} = \dfrac{\$2.54}{x}$